The invention relates to an apparatus for manufacturing a strand formed of reinforcing fibers, such as glass fibers, and fibers formed of an organic thermoplastic material.
The invention is employed with a manufacturing apparatus composed of two installations: the first comprises at least one die, which is supplied with glass, from the orifices of which continuous filaments are mechanically drawn; the second comprises at least one drawing head, which is supplied with organic thermoplastic material, from the orifices of which continuous filaments are mechanically drawn. Such an apparatus is described, for example, in U.S. Pat. No. 5,011,523.
This patent discloses various examples of installations that, when used in combination, are employed for the direct production of a composite strand. Thus, certain installations are equipped in a manner such that the glass filaments that are drawn (whether or not they are combined into strand form) pass through a drawing head that delivers a conical layer of organic filaments.
Glass filaments and organic filaments are drawn at rates that may attain dozens of meters per second. Under such drawing conditions, the air in the vicinity of the filaments is propelled and moves in a more or less disorderly manner in proximity of the fiber extrusion installations. When glass filaments and organic filaments are drawn in a manner such that they travel along coaxial paths, the air flow in the entire drawing area is particularly pronounced. This applies particularly to the area of the drawing head which delivers organic filaments. This drawing head and the surrounding equipment presents an obstacle to the flow of air induced by the different filaments. This produces a convection current which is relatively poorly controlled, especially near the area where the organic filaments are drawn. This phenomenon interferes with the cooling of the filaments and may produce fluctuations in the diameter of the drawn filaments, and even breakage of one or more filaments. This results in a localized variation in the percentage of organic material in relation to glass, which may present a disadvantage when the manufactured composite strand is employed for the direct production of a composite material.